UINavigationController：对所有弹出视图控制器的视图应用通用填充/边距

Question

我有一个UINavigationController，并且我希望弹出到堆栈中的每个视图控制器的视图都具有一个共同的填充/边距（例如，所有边均为 25 像素）。实现这一目标的最佳方法是什么？

我原本以为我可以实现UINavigationControllerDelegate，并在navigationController:didShowViewController:animated 或navigationController:willShowViewController:animated 方法中，只需更改即将显示的视图控制器的框架。不过，这似乎没有效果。

我尝试在视图控制器的 viewDidAppear 和 viewWillAppear 方法中做同样的事情，但这也没有用。理想情况下，无论如何我都不想在控制器中添加任何逻辑，因为它们可能并不总是在导航控制器中使用。

我还没有尝试过的最后一个想法是创建一个“包装器”UIViewController，它实际上会被推送到这个堆栈上。这个包装器会将真实视图控制器的视图添加为带有可提供所需边距的框架的子视图。这里的缺点是我需要继承UINavigationController 并覆盖pushViewController:animated，包装器将被初始化和推送。 Apple 的文档表明 UINavigationController 不应该被子类化。

提前致谢。

Answer 1

我通过在UIViewController 的view 周围放置一个“包装器”UIView 而不是UIViewController 本身解决了这个问题。然后包装视图通过在layoutSubviews 方法中设置子视图的框架来填充子视图。

为了方便起见，我附上了我使用的代码。要使用，请将您的UINavigationController 替换为PaddedNavigationController，并设置PaddedNavigationController 的insets 属性。

PaddedNavigationController.h:

#import <Foundation/Foundation.h>

@interface PaddedNavigationController : UINavigationController
{
    UIEdgeInsets _insets;
}

@property (nonatomic, assign) UIEdgeInsets insets;

@end

PaddedNavigationController.m:

#import "PaddedNavigationController.h"

@interface PaddedView : UIView
{
    UIView *_view;
    UIEdgeInsets _insets;
}

@property (nonatomic, assign) UIEdgeInsets insets;

+ (PaddedView *) wrapView:(UIView *)view withInsets:(UIEdgeInsets)insets;
- (id) initWithView:(UIView *)view insets:(UIEdgeInsets)insets;

@end


@implementation PaddedNavigationController

@synthesize insets = _insets;

- (void) pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    //check if the UIViewController's view has already been wrapped by the PaddedView; don't want to wrap it twice
    if(![viewController.view isKindOfClass:[PaddedView class]])
    {
        viewController.view = [PaddedView wrapView:viewController.view withInsets:self.insets];
    }
    [super pushViewController:viewController animated:animated];
}

- (void) setInsets:(UIEdgeInsets)insets
{
    _insets = insets;

    //loop through this navigation controller's view controllers and set the new insets on any PaddedViews
    for(UIViewController *viewController in self.viewControllers)
    {
        if([viewController.view isKindOfClass:[PaddedView class]])
        {
            PaddedView *padded = (PaddedView *)viewController.view;
            padded.insets = insets;
        }
    }
}

@end


@implementation PaddedView

@synthesize insets = _insets;

+ (PaddedView *) wrapView:(UIView *)view withInsets:(UIEdgeInsets)insets
{
    return [[[PaddedView alloc] initWithView:view insets:insets] autorelease];
}

- (id) initWithView:(UIView *)view insets:(UIEdgeInsets)insets
{
    if(self = [super initWithFrame:view.frame])
    {
        _insets = insets;
        self.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleHeight;
        _view = [view retain];
        [self addSubview:view];
    }
    return self;
}

- (void) dealloc
{
    [_view release];
    [super dealloc];
}

- (void) layoutSubviews
{
    //apply the insets to the subview
    _view.frame = CGRectMake(self.insets.left, self.insets.top, self.frame.size.width - self.insets.left - self.insets.right, self.frame.size.height - self.insets.top - self.insets.bottom);
}

- (void) setInsets:(UIEdgeInsets)insets
{
    _insets = insets;
    //we need to re-layout the subviews as the insets have changed
    [self layoutSubviews];
}

@end